Numerical Modeling and Experimental Investigation of Large Deformation Under Static and Dynamic Loading
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Master’s Thesis in Sustainable Structural Engineering Numerical modeling and experimental investigation of large deformation under static and dynamic loading Author: Benjamin Bondsman Supervisors: Björn Johannessona Andreas Linderholtb Assistant: Winston Mmari Examinator: Björn Johannesson Course code: 5BY31E Semester: VT 2021, 30 credits aDepartment of Building Technology bDepartment of Mechanical Engineering Faculty of Technology Numerical modeling and experimental investigation of large deformation under static and dynamic loading Benjamin Bondsman Linnaeus University Faculty of Technology Sustainable Structural Engineering master’s programme 2021 Benjamin Bondsman Numerical modeling and experimental investigation of large deformation under static and dynamic loading This work concludes the two years (120 ECTS) Master’s programme in Sustainable Structural Engineering at Linnaeus Univer- sity in Växjö, Sweden. The work has been performed during the Spring 2021. Field of research: Continuum Mechanics Author: Benjamin Bondsman 2021 Acknowledgement This work is result of numerous comprehensive and extensive lectures and supervision given by Professor Björn Johanesson, whom i find to exemplify the most significant quali- ties & characteristics a teacher and mentor should possess. In this spirit, I’d like to express my sincere gratitude to Prof. Björn Johannesson for his unwavering support throughout of the work. I wish to extend my deepest gratitude and appreciation to my supervisor Associate Professor Andreas Linderholt for his relentless support, insightful suggestions, invaluable guidance and being a tremendous mentor. Besides my supervisors, I’d also like to thank PhD student Winston Mmari for technical consultation and Laboratory Tech- nician Mats Almström for his assistance in setting up the laboratory equipment. Benjamin Bondsman June 7, 2021 Abstract Small kinematics assumption in classical engineering has been in the center of consider- ation in structural analysis for decennaries. In the recent years the interest for sustainable and optimized structures, lightweight structures and new materials has grown rapidly as a consequence of desire to archive economical sustainability. These issues involve non-linear constitutive response of materials and can only be accessed on the basis of geometrically and materially non-linear analysis. Numerical simulations have become a conventional tool in modern engineering and have proven accuracy in computation and are on the verge of superseding time consuming and costly experiments. Consequently, this work presents a numerical computational framework for modeling of geometrically non-linear large deformation of isotropic and orthotropic materials under static and dynamic loading. The numerical model is applied on isotropic steel in plane strain and orthotropic wood in 3D under static and dynamic loading. In plane strain Total Lagrangian, Updated Lagrangian, Newmark-β and Energy Conserving Algorithm time- integration methods are compared and evaluated. In 3D, a Total Lagrangian static ap- proach and a Total Lagrangian based dynamic approach with Newmark-β time-integration method is proposed to numerically predict deformation of wood under static and dynamic loading. The numerical model’s accuracy is validated through an experiment where a knot-free pine wood board under large deformation is studied. The results indicate accu- racy and capability of the numerical model in predicting static and dynamic behaviour of wood under large deformation. Contrastingly, classical engineering solution proves its inaccuracy and incapability of predicting kinematics of the wood board under studied conditions. Keywords: Total Lagrangian, Updated Lagrangian, Newmark, Energy Conserving, Al- gorithm, Numerical, Modeling, Large, Deformation, steel, Wood, Pine, Plane Strain, 3D. Numerisk modellering och experimentell undersökning av stora deformationer vid statisk och dynamisk belastning Benjamin Bondsman Linnéuniversitetet Fakulteten för teknik Hållbar konstruktionsteknik, masterprogram 2021 Abstrakt Små kinematikantaganden inom klassisk ingenjörsteknik har varit centralt för kon- struktionslösningar under decennier. Under de senaste åren har intresset för hållbara och optimerade strukturer, lättviktskonstruktioner och nya material ökat kraftigt till följd av önskan att uppnå ekonomisk hållbarhet. Dessa nya konstruktionslösningar involverar icke- linjär konstitutiv respons hos material och kan endast studeras baserad på geometriskt och materiellt olinjär analys. Numeriska simuleringar har blivit ett konventionellt verktyg inom modern ingenjörsteknik och visat sig ge noggrannhet i beräkning och kan på sikt ersätta tidskrävande och kostsamma experiment. Detta examensarbete presenterar ett numeriskt beräkningsramverk för modellering av geometrisk olinjäritet med stora deformationer hos isotropa och ortotropa material vid statisk och dynamisk belastning. Den numeriska modellen appliceras på isotropiskt stål i plantöjning och ortotropisk trä i 3D vid statisk och dynamisk belastning. I fallet med plantöjning jämförs och utvärderas den Totala Lagrangianen, Uppdaterade Lagrangianen, Newmark-β och Energi Konserverings Algoritm metoderna. I 3D föreslås en statisk Total Lagrangian metod och en dynamisk Total Lagrangian-baserad metod med Newmark-β tidsintegreringsmetod för att numeriskt förutse statisk och dynamisk deformation hos trä. Den numeriska modellens noggrannhet valideras genom ett experiment där en kvist- fri furuplanka studeras under stora deformationer. Resultaten bekräftar noggrannhet och förmåga hos den numeriska modellen att förutse statiska och dynamiska processer hos trä vid stora deformationer. Däremot, visar klassisk ingenjörslösning brist på förmåga att förutse trä plankans kinematik under studerade förhållanden. Keywords: Total Lagrangian, Updated Lagrangian, Newmark, Energi, Konservering, Algoritm, Numerisk, Modellering, Stora, Deformationer, Stål, Trä, Furu, Plantöjning, 3D. List of Figures Figure 1 – Narrow Bridge collapse in 1940 [3]. .................... 12 Figure 2 – Collapse of (a) Maskinhallen and (b) Siemens Arena [16],[10]. 13 Figure 3 – Geometry & mechanical description of a steel cantilever in 2D. 15 Figure 4 – Geometry & mechanical description of wood board in 3D. 15 Figure 5 – Illustration of motion of a continuum material body. .......... 19 Figure 6 – Illustration of internal material response in section plane: (a) Material body under external loads; (b) Resulting internal material forces; (c) Internal forces in static equilibrium..................... 25 Figure 7 – Linearization................................. 34 Figure 8 – Illustration of Lagrangian mesh....................... 36 Figure 9 – Illustration of Lagrangian (L) and Eulerian (E) mesh........... 37 Figure 10 – (a) Undamped and (b) damped material response under dynamic load. 40 Figure 11 – Stability diagram of Newmark-β Method. ................ 45 Figure 12 – Stress-strain curve.............................. 51 Figure 13 – Illustration of anisotropy and orthotropy.................. 52 Figure 14 – Orthotropic directions............................ 52 Figure 15 – Coordinate transformation of annual rings in wood............ 53 Figure 16 – Illustration of mathematical coordinate transformation.......... 53 Figure 17 – Element coordinate transformation .................... 56 Figure 18 – Coordinate transformation of annual rings in wood in 2D. 57 Figure 19 – Illustration of annual rings pith variation along length of a wood board. 58 Figure 20 – Geometry and mathematical description of coordinate transformation of wood in 3D. ............................... 59 Figure 21 – Illustration of (a) triangular mesh and (b) tetrahedral mesh. 70 Figure 22 – Illustration of 2D FEM triangular element................. 71 Figure 23 – Illustration of 3D FEM tetrahedral element................ 72 Figure 24 – (a) Analytical integration and (b) numerical integration. 93 Figure 25 – Schematic illustration of Newton-Raphson scheme. ........... 96 Figure 26 – Illustration of cantilever geometry in 2D.................. 99 Figure 27 – FEM model of steel cantilever in 2D with triangular mesh elements. 99 Figure 28 – Illustration of experimental model of the wood board. 100 Figure 29 – FEM model of the wood board with tetrahedral mesh elements. 101 Figure 30 – Experimental setup of mechanical clamp. 106 Figure 31 – Experiment design strategy.........................107 Figure 32 – Non-linear static deformation in Total Lagrangian (TL) and Updated Lagrangian (UL) with colormap of axial stresses in [MPa]. 109 Figure 33 – Linear static deformation with colormap of axial stresses in [MPa]. 109 Figure 34 – Comparison of horizontal displacement inTL,UL vs. linear solution. 110 Figure 35 – (a) horizontal and (b) vertical static reaction forces in plane strain. 110 Figure 36 – (a) horizontal and (b) vertical static internal forces in plane strain. 111 Figure 37 – (a) axial (b) transversal and (c) shear strains in plane strain (static). 111 Figure 38 – (a) axial (b) transversal and (c) shear stresses in plane strain (static). 112 Figure 39 – Dynamic motion ofTL andUL solution in Newmark- β scheme with colormap of axial stresses in [MPa].....................113 Figure 40 – Dynamic motion of linear engineering solution in Newmark-β scheme with colormap of axial stresses in [MPa]. 113 Figure 41 – (a) Vertical (b) horizontal displacement of Linear and non-linear Newmark- β method vs. non-linear Energy Conserving Algorithm. 114 Figure 42 – (a) horizontal and